1. Technical Field:
The invention relates to radiation diagnostics and more particularly to an improved method and apparatus for locating an internal breast lesion along three-dimensional coordinates by radiologic examination and quickly and accurately inserting the tip of a needle in the lesion for performing a biopsy or marking the lesion's location by means of a dye or guide wire.
2. Description of the Prior Art:
Breast cancer is one of the leading causes of death in women in the United States. In 1983, there were 114,000 new cases of breast cancer in this country which represented about 26% of all new cancer cases in women. By far the most useful technique in early detection is mammography, radiological examination of the breast to discover the existence and location of a lesion or "lump". Once a lesion is located, it is then necessary to obtain a tissue sample for examination, or biopsy, so as to determine the nature of the lesion, e.g. benign or malignant.
Generally, the methods available to obtain a tissue sample of the lesion, or cells from the tissue, include surgical excision or needle biopsy and aspiration. Before surgery can be performed, the lesion must be located so that a visual tract can be seen from the surface of the skin to the lesion. Such a tract is generally marked by a thin guide wire placed in the tissue or a blue dye injected into the tissued along the tract.
However, multiple attempts at inserting the needle for placing the wire or dye are invariably required. This is due to the fact that the breast has neither a fixed shape nor reliable constant landmarks other than the nipple. It must be maintained in relatively strict confinement during location of the lesion or, with almost any movement of the patient, it will deform and render meaningless and three-dimensional coordinates for locating the lesion therein. Repeated decompression and recompression exacerbate the difficulties greatly by making it extremely difficult to accurately and precisely reproduce needle placement.
Similarly, needle biopsy and aspiration requires extreme accuracy and several attempts at needle placement is both traumatic for the patient and time consuming. Some attempts have been made at employing compression grids with very limited success. Current compression grids only measure in two dimensions and depth is left to be estimated based on the preliminary mammogram, where the breast was compressed in an orthogonal direction to the direction of needle placement compression.
In attempt to reduce artifacts in the mammogram associated with subject motion and X-ray scattering, compression mammography was developed wherein the breast is held in compression between two plates while an x-ray is taken. Various designs for such a compression apparatus have been developed and some representative examples are illustrated in U.S. Pat. Nos. 4,599,738 to Panetta, et al.; 4,259,585 to Novak, et al.; and 4,573,180 to Summ.
Panetta discloses a wall mounted system which provides for magnified as well as non-magnified compression examination of a female breast for multiple positions while the patient remains seated or standing. Novak discloses an apparatus which holds the breast in compression and has a marking or scale on the upper compression plate which is reproducible on the x-ray film and therefore locates the lesion, but in the X-Y plane only. Summ discloses a motor driven compression apparatus for preparing normal or enlarged x-ray images.
Granger, U.S. Pat. No. 1,370,640, discloses an apparatus for localizing foreign bodies wherein the patient lies on a table having a transparent top and a movable x-ray source therebelow. The x-ray source is moved until the shadow of the foreign body being searched for is located in a small fluorescent area of a screen positioned above the patient. A localizer plate is then slipped between the patient and the table and is positioned so that the shadow is seen lying directly over a cross within a small hole in the localizer plate.
The x-ray source is then moved until the shadow of the foreign body is seen to leave the central area of the cross and assure a similar position with respect to a lateral area of the cross. A pointer on a vertical scale between the fluorescent plate and the vertical plate is then raised until its shadow blends with the shadow of the lateral area of the cross. The pointer now lies on a vertical plane with the foreign body and a small mark can be made on the skin at the cross to indicate the location of the foreign body in the X-Y plane as well as at the end of the pointer to indicate the vertical position of the foreign body.
Only one of these patents, Granger, provides for the three-dimensional location of a foreign body. However, it is clear that the system of Granger has at least two disadvantages when applied to mammography. First there is the affect of even the slightest movement by the patient on the table, which could cause a locating mark to be made in the wrong spot on the skin.
Second, the x-ray source must move in relation to the x-ray film. Dedicated mammography equipment in use today employs an x-ray source which is fixed in a substantially perpendicular relation to the x-ray film. Therefore, the apparatus of Granger could not be employed with available mammography equipment.
Another attempt at location of a breast lesion is described in Price, J. L. and Butler, P. D., Stereoscopic Measurement in Mammography, Proc. of the British Inst. of Radiology, p. 901, Nov. 1971. The method employed involves two exposures taken from a superior-inferior position with the x-ray tube displaced 7 centimeters between exposures. These exposures are viewed and aligned together on a mirror stereoscope and then aligned with the lesion. Two parallax readings are taken from which the depth of the lesion is calculated according to formulae described therein. The difficulty of practising this technique with the currently available fixed source equipment is apparent.
Another serious consideration in mammography is the diagnosis of a lesion once located. The best method of forming such a diagnosis is to sample and test, a portion of the tissue from the actual lesion. The obvious aim is to sample the lesion tissue with the least discomfort to the patient. This usually entails a procedure along the lines of a needle biopsy in which a hollow needle is inserted into the tumor or lesion and a sample of the tissue is drawn out, either with the needle after detachment by rotation, or by other means such as aspiration.
A number of devices have been proposed to facilitate needle placement. These are often referred to as stereotaxic devices and are exemplified in U.S. Pat. Nos. 4,583,538 to Onik, et al.; 3,817,249 to Nicholson; 4,580,561 to Williamson; and 4,427,005 to Tener.
Onik, in FIG. 6 and the accompanying text, discloses a device for positioning a biopsy needle in three-dimensions which requires computed tomography to initially locate the lesion. The device of Nicholson is for positioning electrodes in the x-y plane only.
Williamson discloses an apparatus employing two parallel compression grids which are used to direct interstitial implants through the breast along a line normal to the plates. Tener discloses a template for controlling the location and placement of needles in a breast in preparation for placing radioactive seeds.
Clearly it is desirable to insert the needle and draw the sample as expeditiously as possible. This requires extreme accuracy both in location of the lesion as well as subsequent placement of the needle, both of which are greatly complicated by the pliancy of the breast. Furthermore, when location of the lesion and placement of the needle are performed in two separate operations, as is suggested by the references above which generally disclose either means for locating the lesion or for placing the needle, the problem is exacerbated greatly.
Attempts have been made to combine the two functions specifically in the area of breast lesions. One such apparatus is marketed under the name TRC MAMMOTEST by Tekniska Rontgencentralen AB, P.O. Box 121, S-183 22 TABY, Sweden. The development of the instrument is described by Bolmgren, Jacobson and Nordenstrom in Stereotaxic Instrument for Needle Biopsy of the Mamma, The J. Roentgenol., 129:121-125, July 1977 and some of its methods are employed in Svane, G., A Stereotaxic Technique for Preoperative Marking of Non-Palpable Breast Lesions, Acta Radiologica Diagnosis, 24, (1983) Fasc. 2, pp. 145-151.
With the MAMMOTEST, the patient lies face down in a prone position on a horizontal platform mounted above the instrument with the involved breast hanging through a hole in the platform and compressed between two plates. Two x-ray exposures through the breast are taken by rotating the x-ray source to plus or minus 15.degree. from the line normal to the center of the film plate. A digital computer is then utilized to compute mathematical expressions for the coordinates of the lesions according to complex formulae set forth and explained in the Bolmgren publication.
Another method of location and needle placement is described in Yagen, et al. Mammographic Needle Localization of Lesions Seen In Only One View, Amer. J. Roentgenology, 144:911-916, May 1985. Briefly, the Yagen technique involves a preliminary mammogram taken preferably of a mediolateral view to determine the point of entry for the localization needle, and over which a small adhesive marker is placed. The x-ray source is then rotated 30.degree. without changing the position of the breast. An exposure is made and the depth of the lesion is calculated as 1.73 times the distance measured between the images of the tape marker and the lesion. The mathematical basis for the factor 1.73 is derived in the publication. A needle and subsequently a guide wire are placed based on the point of entry and the calculated depth. As is apparent from an analysis of FIG. 2 of the reference, Yagan makes the assumption that the x-rays emanating from each position of the tube during a given exposure are parallel to one another at approximately 36 inches from the x-ray source. This assumption is not valid. X-rays do not emanate from a point source as parallel rays but rather spread out with increasing distance from the source. This introduces problems of parallax which could seriously affect the accuracy of the Yagan device. Furthermore, there is the problem discussed above relating to the natural pliancy of the breast, in which two exposures are taken while attempting to avoid moving the breast. At no time is compression employed.
In addition to the freestanding MAMMOTEST apparatus, Applicant is aware of two other commercially available units designed to fit onto existing mammography equipment. The first is the STEREOTIX instrument for fine needle biopsy put out by CGR skandinaviska ab, Torshamnsgaten 28, Kista, Box 1243, S-163 13 SPANGA, Sweden. This machine is also a digital computer-based apparatus designed to fit specifically on a Thomson CGR Senographe 500T mammography unit.
The other such machine is the CYTOGUIDE put out by Philips which also requires a digital computer for calculation of the coordinates of the lesion. This unit is designed to fit on a Philips mamography unit.
Both the STEREOTIX and the CYTOGUIDE units utilize the same complex mathematical principles explained in the Bolmgren article with respect to the TRC MAMMOTEST. In both the STEREOTIX and the CYTOGUIDE, the patient may be sitting or standing, the breast is compressed between a compression plate and a breast support/film holder, both of which are suspended above what was the original breast support plate of the mammographic unit to which the STEREOTIX or CYTOGUIDE is attached. However, as with the MAMMOTEST, the breast is held stationary while the x-ray source and film plate are rotated to take two views at plus and minus 15.degree. from the orthoganal to the film plate. In all of the above-described prior art units, symmetry of the two views taken is required for accurate computation of the coordinates of the lesion which, for all practical purposes, must be performed by computer.
TRC MAMMOTEST also provides a removable puncture device which is adjusted to the calculated coordinates and then attached to the compression portion of the apparatus. The puncture device does not allow for removal of the needle from the device while its position in the lesion is maintained. This is a considerable disadvantage in that it severely limits the types of tissue sampling techniques available to the physician. Both the STEREOTIX and the CYTOGUIDE also include a puncture apparatus, both of which suffer from the same short-coming as the MAMMOTEST.
There are a number of other disadvantages associated with these commercially available prior art devices. The TCR MAMMOTEST is a very large freestanding device dedicated to the breast lesion localization and needle placement as described. A substantial amount of expensive hospital floor space is therefore required for this very costly machine despite its extremely limited function. Further, as the Bolmgren article notes, patients are chosen who have palpable or non-palpable lesions and who require further cytological study. (Bolmgren, page 121, Procedure). The original, traditional mammogram, in which the lesion is initially identified and preliminarily located, is taken with the patient in a sitting position. However, the MAMMOTEST requires that the patient be prone and face down. Therefore, breast architercture surrounding the lesion may well change rendering visualization on the MAMMOTEST very difficult.
It should be noted that the other two devices, the STEREOTIX and the CYTOGUIDE, are both designed to function with a particular mammography unit and therefore their use is quite limited. Further, even if the facility looking to add such a device already has the appropriate mammography unit, the Applicant is advised that the attachments themselves are extremely costly, in the vicinity of $50,000.00 for the CYTOGUIDE and $60,000.00 for the STEREOTIX.
As noted above, all three units require the use of a digital computer for calculation of the coordinates of the lesion. Besides the expense, this requirement also increases the possibility of inaccuracy or even total disablement of the apparatus based on the computer failure.
All three of the units also require exact positioning of the x-ray source at plus and minus 15.degree. for accurate calculation of coordinates. Even slight misalignment may substantially affect the computations.
Finally, none of these devices allow for release of the needle from the positioning apparatus once it is advanced into the lesion without withdrawing the needle from the lesion. Therefore, only the tissue directly in line above, through and below the lesion can be sampled.
Applicant is aware of one other existing unit but does not know if the unit is commercially available. It is called the MARK 3D Stereographic Breast Biopsy Guide from AB MEDIDE and does not appear to employ the novel apparatus and method described and claimed hereinafter.